This dissertation is a history of how Indigenous people and scholars from the natural and social sciences have engaged one another since the 1950s in Brazil. Through a case study of the Xavante, one of the most intensely studied groups in Central Brazil, it traces the evolution of relationships between researchers and research subjects. Xavante communities began establishing contact with Brazilian national society in the mid-1940s in the wake of settler colonial expansionism. This high-profile process of contact drew interest from researchers, with the first long-term academic ethnographer arriving in 1958. Scholars from across the human sciences followed, particularly from the fields of anthropology, human genetics, and public health. During subsequent decades, the Xavante were constructed as a population, characterized, and circulated internationally in the form of data, biological samples, and publications. In this sense, this story provides a thread to follow the development of twentieth-century approaches to the characterization of human cultural and biological diversity. It is a history of the building of national research institutions in Brazil and a transnational account of knowledge production during the Cold War and after its end. However, by combining the national and transnational with attention to the intimate experience of research, this project traces the history of creation and circulation of academic scholarship back to its origin in the field. As an in-depth examination of the iterative fieldwork that underlay these large-scale processes, this study is locally grounded in the Xavante villages and the interpersonal interactions and labor that form the basis for knowledge production. It shows how Indigenous people have engaged in scientific knowledge making for their own social, economic, and political ends, and have, in the process, shaped the scholars and disciplines that sought to characterize them. It is a history of how researchers and subjects made and remade themselves through the human entanglement of research.